Coiled tubing is a technology that has been expanding its range of application since its introduction to the oil industry in the 1960's. Its ability to pass through completion tubulars and the wide array of tools and technologies that can be used in conjunction with it make it a very versatile technology.
Typical coiled tubing apparatus includes surface pumping facilities, a coiled tubing string mounted on a reel, a method to convey the coiled tubing into and out of the wellbore, such as an injector head or the like, and surface control apparatus at the wellhead. Coiled tubing has been utilized for performing well treatment and/or well intervention operations in existing wellbores such as, but not limited to, hydraulic fracturing, matrix acidizing, milling, perforating, coiled tubing drilling, and the like.
In the oilfield, downhole tools are commonly used to perform measurements and services in wells. These tools are necessarily shaped like the inside of a well, typically long and narrow. The length of these tools is dependent on what function they are to perform, and additional functions typically impart additional length. As more and more sophisticated functions are performed down hole, these tools have grown in length to the point where installing them in the well bore has become a significant challenge in the face of maintaining well control while this is performed. This process of placing tools into the well bore is referred to as deployment.
In spooled conveyance services such as coiled tubing, wireline, and slickline, downhole tools need to be transferred from the reel to inside the well bore. This transfer may be accomplished using a long riser with the conveyance attached to the top of the long riser. In this method, the tools are either pulled into the bottom of this riser, or are assembled into it. The riser is then attached to the well, is pressure tested, then the tools are run into the well. In an embodiment, an ‘easier to run’ service is utilized to place the tools in the well, followed by a ‘harder to run’ service do the running in hole. In this embodiment, the downhole tools are provided with an additional part known as a deployment bar. This deployment bar is intended to provide a surface against which blowout preventers can both grip and seal. In the case where the ‘harder to run’ service is coiled tubing, wireline or slickline may be used to pre-place the tools in the coiled tubing blow out preventer. The deployment bar used will be selected to have a diameter substantially equal to the coiled tubing diameter.
The most complex method of deployment is one in which the tool is moved inside the pressure barrier in sections. Sections of the tool are installed in the well using the riser method and blow out preventer(s) are closed on special areas of the tool (called deployment bars) to seal in the well bore pressure. Once this seal is made, the riser may be de-pressurized and another section of tool may be installed. This method can accommodate much more complex and delicate tools, because the sealing function is only performed on designated areas of the tool. During deployment, some method and/or apparatus must be used to prevent fluid flow across the joints in the tool during deployment.
It remains desirable to provide improvements in oilfield surface equipment and/or downhole assemblies such as, but not limited to, methods and/or systems for deploying coiled tubing into wellbores.